119 lines
2.9 KiB
C
119 lines
2.9 KiB
C
#define _GNU_SOURCE
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#include <unistd.h> /* usleep() */
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#include <stdio.h>
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#include "lis3dh.h"
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#include "interrupt.h"
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#include "i2c.h"
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/* LIS3DH INT2 connected to Raspberry Pi GPIO 16 (Pin 36) */
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#define GPIO_INTERRUPT_PIN_INT2 16
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int main() {
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lis3dh_t lis;
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lis.dev.init = i2c_init;
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lis.dev.read = i2c_read;
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lis.dev.write = i2c_write;
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lis.dev.sleep = usleep;
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lis.dev.deinit = i2c_deinit;
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/* initialise LIS3DH struct */
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if (lis3dh_init(&lis)) {
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/* error handling */
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}
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/* reset device just in case */
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if (lis3dh_reset(&lis)) {
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/* error handling */
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}
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/* register interrupt on specified pin */
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if (int_register(GPIO_INTERRUPT_PIN_INT2)) {
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/* error handling */
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}
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lis.cfg.mode = LIS3DH_MODE_HR;
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lis.cfg.range = LIS3DH_FS_2G;
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lis.cfg.rate = LIS3DH_ODR_400_HZ;
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/* enable ACT function through INT PIN 2 */
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/* interrupts must be used, there is no reg to poll */
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lis.cfg.pin2.act = 1;
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/* This functionality cannot be filtered internally !! */
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/* 1 LSb = 16 mg @ FS_2G
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* 1 LSb = 32 mg @ FS_4G
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* 1 LSb = 62 mg @ FS_8G
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* 1 LSb = 186 mg @ FS_16G
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*
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* @ FS_2G
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* Wake up when acceleration goes above 1.3g .. (any axis)
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* 1.3g / 16mg = 1300/16 = N LSb = 81.25 ~ 81
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*/
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/* This controls activity recognition */
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lis.cfg.act_ths = 81; /* 7-bit ; must be > 1*/
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/* Sleep-to-wake and return-to-sleep duration
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* 1 LSb = (8 * 1[LSb] + 1) / ODR
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* Confusing formulation !
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*
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* [ODR] [1 LSb in milliseconds]
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* 1 1000
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* 10 100
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* 25 40
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* 50 20
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* 100 10
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* 200 5
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* 400 2.5
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*
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* Full table in lis3dh.h
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*
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* 1 LSb = (8 * N[2.5ms] + 1) / ODR ( @ ODR=400Hz )
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* 1 LSb = (8 * N[LSb] + 1) / ODR ( @ ODR=400Hz )
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*
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* So, 5000 ms => (8 * N[2.5] + 1) / ODR ; solve N=time(ms)/2.5
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* => (8 * 2000[LSb] + 1) / ODR
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* => (8 * 2000 + 1) / ODR
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* => 16001 / 400
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* => 40
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*
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* After `act_ths' worth of acceleration has been felt;
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* Stay in Wake mode for 5000 ms
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*/
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/* This controls return-to-sleep */
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lis.cfg.act_dur = 40; /* 8-bit ; range 0-255 */
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/* write device config */
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if (lis3dh_configure(&lis)) {
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/* error handling */
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}
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for ( ;; ) {
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/* wait until INT2 goes active (Wake mode) */
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if (int_poll(GPIO_INTERRUPT_PIN_INT2)) {
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/* error handling */
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}
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/* Do "work" here at high ODR, HR mode, etc. */
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puts("I am awake!");
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/* wait until INT2 goes inactive (Sleep mode) */
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if (int_poll(GPIO_INTERRUPT_PIN_INT2)) {
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/* error handling */
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}
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puts("Sleeping...");
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}
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/* deinitalise struct */
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if (lis3dh_deinit(&lis)) {
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/* error handling */
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}
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return 0;
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} |